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20(S)-protopanaxatriol (PPT) is a kind of tetracyclic triterpenoid, which is found in the roots of ginseng. It is well known as a potential herbal medicine or healthcare product. However, given its poor water solubility, its application has been limited. In this study, we successfully synthesized a novel mono-[6-(N,N-bis(3-aminopropyl)ethylenediamine)-6-deoxy]-β-cyclodextrin. We prepared inclusion complexes of PPT with three polyamine-modified β-cyclodextrins (CDs) (H1, H2, and H3) of different lengths by the coprecipitation method, aiming at enhancing the aqueous solubility of PPT. The host–guest inclusion complexes of H1, H2, and H3 with PPT were characterized via 1H NMR, XRD, FT-IR spectra, and SEM technology, and the inclusion modes were analyzed by 2D ROESY. The stability constant (Ks), inclusion ratios, and solubility of H1, H2, and H3 with PPT were determined via the phase solubility method. The stability constants (K1:1) were found to be 182.6, 94.2, and 524.4 M−1 for H1/PPT, H2/PPT, and H3/PPT inclusion complexes, with AL-, AN-, and BS-type curves, respectively. That is, when the stoichiometric ratio was 1:1, H3 (with longest-length chain) displayed the strongest binding ability with PPT. The host–guest size/shape-fit relationship and hydrogen bond interaction play a role in improving the stability of H1/PPT, H2/PPT, and H3/PPT inclusion complexes. Through complexation with H1, H2, and H3, the apparent solubility of PPT was obviously increased from the initial value of 0.062 mg/L to 5.1, 3.0, and 7.5 g/L, respectively. Among the three CDs, the solubilization effect of PPT with H3 was the best. Furthermore, H1/PPT, H2/PPT, and H3/PPT inclusion complexes exhibited some activity in inhibiting LPS-induced nitric oxide (NO) generation in macrophages. This satisfactory aqueous solubility and higher stability of H1/PPT, H2/PPT, and H3/PPT inclusion complexes should be possibly useful for its utilization as a herbal medicine and healthcare product. [ABSTRACT FROM AUTHOR]

The effect of exogenous applied nitric oxide on photosynthesis under heat stress was investigated in rice seedlings. High temperature resulted in significant reductions of the net photosynthetic rate ( PN) due to non-stomatal components. Application of nitric oxide donors, sodium nitroprusside (SNP) or S-nitrosoglutathione (GSNO), dramatically alleviated the decrease of PN induced by high temperature. Chlorophyll fluorescence measurement revealed that high temperature caused significant increase of the initial fluorescence ( Fo) and non-photochemical quenching (NPQ) whereas remarkable decrease of the maximal fluorescence ( Fm), the maximal efficiency of PSII photochemistry ( Fv/ Fm), the actual PSII efficiency (Φ PSII), and photochemical quenching ( qp). In the presence of SNP or GSNO pretreatment, the increase of Fo and decrease of Fm, Fv/ Fm, Φ PSII and qp were markedly mitigated, but NPQ was further elevated. Moreover, with SNP or GSNO pretreatment, H 2O 2 accumulation and electrolyte leakage induced by heat treatment were significantly reduced, whereas zeaxanthin content and carotenoid content relative to chlorophyll were elevated. The potassium salt of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a specific NO scavenger, arrested NO donors mediated effects. These results suggest that NO can effectively protect photosynthesis from damage induced by heat stress. The activation effect of NO on photosynthesis may be mediated by acting as ROS scavenging, or/and alleviating oxidative stress via maintaining higher carotenoid content relative to chlorophyll or/and enhancing thermal dissipation of excess energy through keeping higher level of zeaxanthin content under heat stress. [ABSTRACT FROM AUTHOR]